The present invention relates to an electronic device such as a personal computer or digital audio-visual device (AV device) having a data transmission function using an IEEE 1394 bus, and a power source control method therefor.
An IEEE 1394 bus (IEEE Std 1394-1995, Standard for a High Performance Serial Bus) is a serial bus used in, e.g., exchanging digital data between a plurality of digital devices or forming a network for allowing a plurality of digital devices to control each other.
Serial buses include a USB bus (Universal Serial Bus) in addition to the IEEE 1394 bus. While the maximum data transfer rate of the IEEE 1394 bus is 400 Mbps, that of the USB bus is as low as 12 Mbps. Thus, the USB bus is not suitable for a transmission medium for video data of a large information amount. At present, therefore, the IEEE 1394 bus is generally used to form an AV device network.
The network formed by the IEEE 1394 bus has a branch structure in which a given digital device may mediate data transmission between two other digital devices. For this reason, even when the given digital device is no longer used, all the functions of this digital device cannot be stopped.
If, however, the power source of the digital device in such state is erroneously turned off, power applied to a protocol layer formed to control data transmission using the IEEE 1394 bus is entirely stopped. That is, data transmission between the two other digital devices via the given digital device is interrupted and cannot be restored.
The present invention has been made in consideration of the above situation, and has as its object to provide an electronic device for preventing interruption of data transmission between other electronic devices owing to user""s carelessness, and a power source control method therefor.
To achieve the above object, according to the present invention, power applied to a protocol layer formed to control data transmission using an IEEE 1394 bus is controlled independently of a physical layer and other layers. When power-off of a device is instructed, the connection arrangement of a device on a network formed by the IEEE 1394 bus is determined to determine from the determination result whether the device acts as a role of mediation in data transmission between other devices.
When the device is determined to act as a role of mediation in data transmission, power applied to the protocol layer except the physical layer is turned off. When the device is not determined to act as a role of mediation in data transmission, power applied to the protocol layer including the physical layer is turned off.
Even if the power source of the device is erroneously turned off, the device can mediate data transmission between other devices so long as power can be kept applied to the physical layer.
For this reason, in the present invention, when data transmission between other devices is free from any interruption, power applied the protocol layer including the physical layer is turned off. When data transmission between other devices may be interrupted, power applied to the protocol layer except the physical layer is turned off.
In other words, the present invention realizes more appropriate power source control which does not influence data transmission between other devices.
According to the present invention, power applied to the protocol layer formed to control data transmission using the IEEE 1394 bus is controlled independently of the physical layer and other layers. When power-off of the device is instructed, whether to turn off power applied to the physical layer of the protocol layer is inquired. If power-off of the physical layer is instructed in accordance with the inquiry, power applied to the protocol layer including the physical layer is turned off. If keeping power applied to the physical layer is instructed, power applied to the protocol layer except the physical layer is turned off.
In the present invention, when the power source of the device is turned off, it is asked whether to turn off/keep power applied to the physical layer which can mediate data transmission between other devices. This can prevent interruption of data transmission between other devices owing to user""s carelessness.
Moreover, the present invention adopts a back-up battery for applying power to the physical layer of the protocol layer formed to control data transmission using the IEEE 1394 bus while the device is OFF.
According to the present invention, a user can turn off an electronic device regardless of whether or not the electronic device acts as a role of mediation in data transmission between other devices.
According to the first aspect of the present invention, there is provided an electronic device having a data transmission function using a network bus, comprising
a power source control circuit for controlling, independently of a physical layer and other layers, power applied to a protocol layer for controlling data transmission using the network bus,
a determination section for determining a connection arrangement of the device on a network formed by the network bus, and
a power source management section for, when power-off of a device is instructed, determining from a determination result of the determination section whether the device acts as a role of mediation in data transmission between other devices, when the device is determined to act as a role of mediation in data transmission, causing the power source control circuit to turn off power applied to the protocol layer except the physical layer, and when the device is determined not to act as a role of mediation in data transmission, causing the power source control circuit to turn off power applied to the protocol layer including the physical layer.
According to the second aspect of the present invention, there is provided an electronic device having a data transmission function using a network bus, comprising
a power source control circuit for controlling, independently of a physical layer and other layers, power applied to a protocol layer for controlling data transmission using the network bus,
a user interface section for, when power-off of a device is instructed, inquiring whether to turn off power applied to the physical layer of the protocol layer, and
a power source management section for, when power-off of the physical layer is instructed in accordance with the inquiry from the user interface section, causing the power source control circuit to turn off power applied to the protocol layer including the physical layer, and when keeping power applied to the physical layer is instructed, causing the power source control circuit to turn off power applied to the protocol layer except the physical layer.
According to the third aspect of the present invention, there is provided an electronic device having a data transmission function using a network bus, comprising
a power source control circuit for controlling, independently of a physical layer and other layers, power applied to a protocol layer for controlling data transmission using the network bus,
a determination section for determining a connection arrangement of the device on a network formed by the network bus,
a user interface section for inquiring whether to turn off power applied to the physical layer of the protocol layer,
a first power source management section for, when power-off of a device is instructed, determining from a determination result of the determination section whether the device acts as a role of mediation in data transmission between other devices, when the device is determined not to act as a role of mediation in data transmission, causing the power source control circuit to turn off power applied to the protocol layer including the physical layer, and when the device is determined to act as a role of mediation in data transmission, causing the user interface section to inquire whether to turn off power applied to the physical layer of the protocol layer, and
a second power source management section for, when power-off of the physical layer is instructed in accordance with the inquiry from the user interface section, causing the power source control circuit to turn off power applied to the protocol layer including the physical layer, and when keeping power applied to the physical layer is instructed, causing the power source control circuit to turn off power applied to the protocol layer except the physical layer.
According to the fourth aspect of the present invention, there is provided an electronic device having a data transmission function using a network bus, comprising
a control circuit for, when power-off is instructed, turning off power applied to a physical layer of a protocol layer for controlling data transmission using the network bus, and
a back-up power source for applying power to the physical layer when the control circuit turns off power applied to the physical layer.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.